The major objectives are: (1) Formulation of a molecular mechanism for the control of the fatty acid composition of membrane lipids. Experiments indicate that temperature-responsive homeostatic control is non-nonenzymatic, and is inherent in the bilayer itself. Corollaries are a molecular mechanism to explain positional specificity and for temperature effects upon the composition of fats and waxes in higher organisms. (2) Clarification of the structure of serum lipoproteins. Experiments indicate that cholesterol esters in these particles behave thermodynamically as a bulk liquid-crystalline phase, and may require re-evaluation of current concepts of lipoprotein structure. (3) The finding that asymmetric lipid bilayers can undergo separate transitions on each side will be continued with model systems, expanded to real membranes, and, hopefully, used as a tool to investigate transport properties. (4) The role of glycolipids as a stabilizing factor in membranes rich in acidic phospholipids will be studied as a first step in understanding the lipid class composition of membranes. (5) The effects of anaesthetics and related small molecules upon the volume of membranes and model systems will be studied, with special emphasis upon the critical volume hypothesis for anaesthetic action. (6) A search will be made for higher-order transitions in membranes and model systems, with special emphasis upon the possibility of glass transitions in cholesterol-rich membranes. If such transitions exist, they should be extremely informative structurally. Techniques will include a wide variety of physical approaches, but differential scanning calorimetry and dilatometry will be emphasized.